When a person walks, their foot repeatedly pronates and supinates. This is normal. The biomechanics of a person's stride, including their pronation and supination, are largely dependent upon that person's foot structure. Specifically, foot structure at least partially dictates the duration and amplitude of foot pronation and supination. Structural problems of the foot undesirably can lead to unhealthy pronation, which can produce a number of health problems. For example, excessive and prolonged pronation can lead to hip injury.